--Couldyoujoinusthisafternoon?---Sorry,I

問題詳情：

--Could you join us this afternoon?

---Sorry, I _______.  I          take care of my little sister because my mother is out.

A. can’t; may        B. couldn’t; have to  C. can’t; have to    D. couldn’t; may

【回答】

C

知識點：情態動詞

題型：選擇題